The invention relates to an electromagnetically actuated hydraulic valve switching unit.
An armature plunger reciprocally shuttles between two magnetic paths. A pair of coils are energizable to create magnetic fluxes having portions of their linkage paths in common, including through the plunger. When either coil is energized, a flux path is created around that coil through the plunger, and another flux path is created around both coils through the plunger. The ratio of the permeances of the two paths is controlled such that one path always overpowers the other, to insure plunger movement in either direction.
The armature plunger actuates bistable snap blade means in a hydraulic valve circuit. A housing includes a cavity into which a portion of the armature plunger extends an engages the snap blade. The housing has a hydraulic fluid entry port into the cavity, a hydraulic fluid exit port out of the cavity, and a hydraulic fluid vent port out of the cavity. A first position of the snap blade blocks the vent port and opens the entry port such that hydraulic fluid may flow from the entry port to the exit port. A second position of the snap blade blocks the entry port such that hydraulic fluid may flow from the exit port to the vent port. The preferred embodiment further includes a second vent port comprising an annulus around a shaft segment of the armature within a journaled portion of the housing for venting hydraulic fluid from the cavity along the shaft-journal interface. The preferred emobidment further includes dual snap blades and cavities at opposite ends of the armature plunger for tandem operation of a hydraulic circuit.